System and Method for Orthogonal Frequency Division Multiple Access (OFDMA) Transmission

ABSTRACT

An OFDMA subframe carrying different data fields in different time segments may include a separate short training field (STF), and a separate set of long training fields (LTFs), for each of the data fields to accommodate time-reuse scheduling. Communicating a separate STF for each data field may allow receivers to re-adjust automatic gain control (AGC) when the data fields carry different numbers of space-time-streams. Likewise, communicating separate sets of LTFs for each data field may allow different beamforming parameters to be applied to different data fields.

This patent application is a continuation of U.S. patent applicationSer. No. 16/456,469, filed on Jun. 28, 2019 and entitled “System andMethod for Orthogonal Frequency Division Multiple Access (OFDMA)Transmission,” which is a continuation of U.S. patent application Ser.No. 14/823,801, now U.S. Pat. No. 10,340,964, filed on Aug. 11, 2015 andentitled “System and Method for Orthogonal Frequency Division MultipleAccess (OFDMA) Transmission,” which claims priority to U.S. ProvisionalApplication No. 62/038,778, filed on Aug. 18, 2014 and entitled“Orthogonal Frequency Division Multiple Access (OFDMA) Frame Structuresfor Scheduling of Different Stations in a Sub-Channel, InterleaverDesigns, and Extended Tone Interleaved Long Training Fields (LTFs),”applications of which are hereby incorporated by reference herein as ifreproduced in their entireties.

TECHNICAL FIELD

The present invention relates to telecommunications, and, in particularembodiments, to systems and methods for orthogonal frequency divisionmultiple access (OFDMA) transmission.

BACKGROUND

Orthogonal frequency division multiplexed (OFDM) waveforms are presentlyused to communicate over Evolved Universal Terrestrial Radio Access(E-UTRA) air interfaces in fourth generation (4G) long term evolution(LTE) networks operating under the communications protocol defined bythird generation partnership project (3GPP) technical standard (TS)36.211 (2008), which is incorporated by reference herein as ifreproduced in its entirety. OFDM waveforms provide many advantages overother waveforms, including the ease of implementation using fast Fouriertransform (FFT) and inverse FFT (IFFT) and robustness against multi-pathfading.

SUMMARY OF THE INVENTION

Technical advantages are generally achieved, by embodiments of thisdisclosure, which describe systems and methods for orthogonal frequencydivision multiple access (OFDMA) transmission.

In accordance with an embodiment, a method for performing orthogonalfrequency division multiple access (OFDMA) transmissions is provided. Inthis example, the method includes transmitting a first OFDMA subframeover a wireless network. The first OFDMA subframe carries a first datafield in a first time segment of a first OFDMA sub-channel, a seconddata field in a second time segment of the first OFDMA sub-channel. Thefirst OFDMA subframe further includes a first high efficiency wirelesslocal area network (HE WLAN) (HEW) short training field (STF) for thefirst data field, a first set of HEW long training fields (LTFs) for thefirst data field, a second HEW STF for the second data field, and asecond set of HEW LTFs for the second data field. An base station forperforming this method is also provided.

In accordance with another embodiment, a method for receiving OFDMAtransmissions is provided. In this example, the method includesreceiving an OFDMA subframe carrying a first data field in a first timesegment of an OFDMA sub-channel, and a second data field in a secondtime segment of the OFDMA sub-channel. The OFDMA subframe furtherincludes a first HEW STF for the first data field, a first set of HEWLTFs for the first data field, a second HEW STF for the second datafield, and a second set of HEW LTFs for the second data field. A mobilestation for implementing such method is also provided.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates a diagram of an embodiment wireless communicationsnetwork;

FIG. 2 illustrates a diagram of an embodiment down-link (DL) OFDMA framestructure;

FIG. 3 illustrates a diagram of another embodiment down-link (DL) OFDMAframe structure;

FIG. 4 illustrates a flow chart of an embodiment method for transmittinga down-link (DL) OFDMA subframe;

FIG. 5 illustrates a flow chart of an embodiment method forcommunicating a down-link (DL) OFDMA subframe;

FIG. 6 illustrates a diagram of an embodiment IEEE 802.11 framestructure;

FIG. 7 illustrates a diagram of an embodiment OFDMA frame for aligningthe LTF sections of OFDMA subframes in the time domain;

FIG. 8 illustrates a diagram of an embodiment interleaver design;

FIG. 9 illustrates a graph of simulation results for embodiment longtraining field (LTF) configurations;

FIG. 10 illustrates a diagram of an embodiment acknowledgementprocedure;

FIG. 11 illustrates a diagram of another embodiment acknowledgementprocedure;

FIG. 12 illustrates a diagram of an embodiment processing system; and

FIG. 13 illustrates a diagram of an embodiment transceiver.

Corresponding numerals and symbols in the different figures generallyrefer to corresponding parts unless otherwise indicated. The figures aredrawn to clearly illustrate the relevant aspects of the embodiments andare not necessarily drawn to scale.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of embodiments of this disclosure are discussed indetail below. It should be appreciated, however, that the conceptsdisclosed herein can be embodied in a wide variety of specific contexts,and that the specific embodiments discussed herein are merelyillustrative and do not serve to limit the scope of the claims. Further,it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of this disclosure as defined by the appended claims.

Time-reuse scheduling may allow multiple STAs (or groups of STAs) toreceive data in the same OFDMA subframe by partitioning the payload ofthe OFDMA subframe in the time domain, and then scheduling differentSTAs (or groups of STAs) to receive data fields in different timesegments. Notably, data fields in the same OFDMA subframe may carrydifferent numbers of space-time streams, and may be transmitted usingdifferent beamforming parameters.

Aspects of the present disclosure provide an OFDMA subframe structurethat includes a separate short training field (STF), and a separate setof long training fields (LTFs), for each data field in an OFDMA subframeto accommodate time-reuse scheduling in the OFDMA subframe.Communicating a separate STF for each data field may allow receivers tore-adjust automatic gain control (AGC) when the data fields carrydifferent numbers of space-time-streams. Likewise, communicatingseparate sets of LTFs for each data field may allow differentbeamforming parameters to be applied to different data fields.Throughout this disclosure, the term “a set of LTFs” refers to one ormore LTFs, and should not be interpreted as inferring that multiple LTFsare necessarily included in the set of LTFs. Moreover, the terms“space-time streams” and “TX streams” are used interchangeably.

FIG. 1 illustrates a network 100 for communicating data. The network 100comprises a base station 110 having a coverage area 101, a plurality ofmobile stations (STAs) 120, and a backhaul network 130. As shown, thebase station 110 establishes uplink (dashed line) and/or downlink(dotted line) connections with the mobile stations 120, which serve tocarry data from the mobile stations 120 to the base station 110 andvice-versa. Data carried over the uplink/downlink connections mayinclude data communicated between the mobile stations 120, as well asdata communicated to/from a remote-end (not shown) by way of thebackhaul network 130. As used herein, the term “base station” refers toany component (or collection of components) configured to providewireless access to a network, such as an enhanced base station (eNB), amacro-cell, a femtocell, a Wi-Fi access point (AP), or other wirelesslyenabled devices. Base stations may provide wireless access in accordancewith one or more wireless communication protocols, e.g., long termevolution (LTE), LTE advanced (LTE-A), High Speed Packet Access (HSPA),Wi-Fi 802.11a/b/g/n/ac, etc. As used herein, the term “mobile station”refers to any component (or collection of components) capable ofestablishing a wireless connection with a base station, such as a userequipment (UE), a mobile device, and other wirelessly enabled devices.In some embodiments, the network 100 may comprise various other wirelessdevices, such as relays, low power nodes, etc.

Time domain granularity in the Wi-Fi OFDMA Resource Unit (RU) design wasproposed in U.S. Provisional Patent Application No. 62/028,208 filedJul. 23, 2014 and entitled “System and Method for OFDMA ResourceAllocation” and U.S. Provisional Patent Application No. 62/028,174 filedJul. 23, 2014 and entitled “System and Method for Orthogonal FrequencyDivision Multiple Access,” both of which are incorporated by referenceherein as if reproduced in their entireties. Time granularity providesfor efficient scheduling of STAs with short or long packets in both timeand frequency domains.

When multiple STAs are scheduled in different time segments of asub-channel, different numbers of TX streams may be applied to differentdata fields carried in the different time segments. In this case, it maybe helpful to have a separate short training field (STF) to re-adjustautomatic gain control (AGC) for different time segments. Moreover,since different beamforming (BF) parameters may be applied to thedifferent data fields, it may also be helpful to have a separate set oflong training fields (LTFs) for each data field. FIG. 2 illustrates anembodiment downlink (DL) OFDMA frame structure 200 for accommodatingtime-reuse scheduling. The embodiment DL OFDMA frame structure 200includes a mid-amble type of OFDMA frame structure. As shown, theembodiment DL OFDMA frame structure 200 comprises a plurality of OFDMAsubframes 210, 220, 240 communicated over different sub-channels. Eachof the OFDMA subframes 210, 220, 240 includes a preamble field 252, ahigh efficiency wireless local area network (HE WLAN) (HEW)-SIGA/SIGBfield 254, and a payload. The preamble field 252 may carry informationfor mobile stations operating in accordance with Institute of Electricaland Electronics Engineers (IEEE) 802.11n, such as information related tobase station identification and selection, frame time and frequencysynchronization, and channel estimation. In one example, the preamblefield 252 carries STFs and LTFs in accordance with IEEE 802.11n. Thepayloads of the OFDMA subframes are divided into n time segments 256,258. The payloads of the OFDMA subframes 210, 220, 240 carry HEW STFs211, 221, 241, sets of HEW LTFs 212, 222, 242, and data fields 214, 224,244 in the first time segment 256, and HEW STFs 216, 226, 246, sets ofHEW LTFs 217, 227, 247, and data fields 219, 229, 249 in the second timesegment 258. Each HEW STF and each set of HEW LTFs are used to decodethe data field in their respective sub-channels and time segments.Throughout this disclosure, the terms “HE WLAN” and “HEW” are usedinterchangeably.

As can be seen from FIG. 2, in each time segment, each data field has acorresponding HEW STF and a corresponding set of HEW LTFs right beforethe respective data field, that is, the HEW STF and the set of HEW LTFsprecede the corresponding data field in the time segment. For example,the HEW STF 211 and the set of HEW LTFs 212 of the first time segment256 in the sub-frame 210 precede the data field 214. Likewise, the HEWSTF 216 and the set of HEW LTFs 217 in the second time segment 258precede the data field 219 of the sub-frame 210. Since the AGCre-adjustment is done in the time domain, HEW STFs may be aligned in thetime domain over the whole bandwidth. In the example depicted in FIG. 2,the HEW STFs are aligned in each time segment across the differentsub-channels. In one embodiment, padding may be used to align the end ofthe data fields in a time segment, so that the HEW STFs of the next timesegment can be aligned. In other examples, HEW STFs are not aligned inthe time domain.

FIG. 3 illustrates another embodiment DL OFDMA frame structure 300 foraccommodating the time-reuse scheduling of sub-channels. The embodimentDL OFDMA frame structure 300 includes a multi-amble type of OFDMA framestructure. The DL OFDMA frame structure 300 includes a plurality ofOFDMA subframes 310, 320, 340 communicated over different sub-channels.Each of the OFDMA subframes 310, 320, 340 includes a preamble field 352,a HEW-SIGA/SIGB field 354, and a payload. The preamble field 352 may besimilar to the preamble field 252 in the embodiment DL OFDMA framestructure 200.

The payload of each of the OFDMA subframes 310, 320, 340 carries aplurality of data fields, as well as a separate HEW STF and a separateset of HEW LTFs for each of the data fields. Each data field in asub-channel is carried in a different one of the time segments 362, 364,366. Each HEW STF and set of HEW LTFs includes signaling that is used todecode the corresponding data field. As shown, all of the HEW STFs andHEW LTFs in the OFDMA subframes precede the corresponding data fields.The HEW STF 311, 321, 341 and the sets of HEW LTFs 312, 322, 342 carrysignaling that is used to decode the data fields 315, 325, 345 carriedin the time segment 362, respectively, while the HEW STF 313, 323, 343and the sets of HEW LTFs 314, 324, 344 carry signaling that is used todecode the data fields 316, 326, 346 carried in the time segment 364,respectively.

FIG. 4 is a flow chart illustrating an embodiment method 400 forcommunicating a DL OFDMA frame. The method 400 begins at step 410, wherea base station generates a DL OFDMA sub-frame that carries multiple datafields in different time segments, as well as a separate HEW STF and aseparate set of HEW LTFs for each of the data fields. Each data fieldmay be scheduled to be received by one or more mobile stations, anddifferent data fields may be scheduled to be received by differentmobile stations or groups of mobile stations. Different data fields maybe transmitted using different beamforming parameters. A set of HEW LTFsfor a data field may be transmitted using the same beamformingparameters as the data field. The DL OFDMA sub-frame is then transmittedto the scheduled STAs at step 420.

FIG. 5 is a flow chart illustrating another embodiment method 500 forcommunicating a DL OFDMA sub-frame. The method 500 begins at step 510,where a user equipment receives a DL OFDMA sub-frame that carriesmultiple data fields in different time segments, as well as a separateHEW STF and a separate set of HEW LTFs for each of the data fields. Theuser equipment uses the HEW STFs and the sets of HEW LTFs to decode thecorresponding data fields carried in different time segments at step520.

The OFDMA frame structures described herein are not limited to DLtransmissions, and may be adapted for UL and D2D transmissions. Forexample, an UL OFDMA frame structure similar to that depicted in FIGS.2-3 may be used to accommodate the time-reuse scheduling of differentSTAs per sub-channel. In an embodiment, an Ack message may be firstscheduled in an UL frame for those STAs who have received a DL packet.Thereafter, the time reuse property is used to schedule the UL STAsusing a similar OFDMA frame structure.

In conventional IEEE 802.11 networks, the number of LTFs included in aframe is generally determined by the number of space-time streams (STSs)carried in the frame. More specifically, IEEE 802.11ac requires one LTFfor frames carrying one STS, two LTFs for frames carrying two STSs, fourLTFs for frames carrying three or four STSs, six LTFs for framescarrying five or six STSs, and eight LTFs for frames carrying seven oreight STSs. U.S. patent application Ser. No. 14/720,680 filed on May 22,2015 and entitled “System and Method for OFDMA Resource Allocation”,which is incorporated by reference herein as if reproduced in itsentirety, provides methods to increase channel estimation performance byincluding more LTFs in a frame than required by IEEE 802.11ac for thenumber of STSs carried in the frame. For example, a base station maytransmit at least two LTFs in a frame carrying one STS, at least threeLTFs in a frame carrying two STSs, at least five LTFs in a framecarrying three or four STSs, and at least seven LTFs in a frame carryingfive or six STSs. In such examples, these additional LTFs may provideimproved channel estimation performance.

FIG. 6 is a diagram of an embodiment IEEE 802.11 frame structure 600. Asshown, the frame structure 600 comprises a preamble 610, a VHT preamble615, and VHT data payload 620. The preamble field 610 may be similar tothe preamble field 252 in the embodiment DL OFDMA frame structure 200.The VHT preamble 615 may include multiple VHT-LTFs. The VHT payload 620may carry multiple STSs to STAs in a cell. Channel estimationperformance may be improved by including more VHT-LTFs in the frame thanrequired by IEEE 802.11ac for the number of STSs carried in the frame.For example, a base station may transmit at least two VHT-LTFs 616 in aframe carrying one STS, at least three VHT-LTFs 616 in a frame carryingtwo STSs, at least five VHT-LTFs 616 in a frame carrying three or fourSTSs, at least seven VHT-LTFs 616 in a frame carrying five or six STSs,and at least nine VHT-LTFs 616 in a frame carrying seven or eight STSs.In one embodiment, the VHT-LTFs 616 may include at least two moreVHT-LTFs than STSs carried in the frame. For example, the base stationmay transmit at least four VHT-LTFs 616 in a frame carrying two STSs andat least six VHT-LTFs 616 in a frame carrying three or four STSs. Inanother embodiment, the base station may transmit at least twice as manyVHT-LTFs 616 as STSs used to communicate the frame. For example, thebase station may transmit at least two VHT-LTFs 616 in a frame carryingone STS.

FIG. 7 is a diagram of an embodiment OFDMA frame 700 for aligning LTFsections of OFDMA subframes in the time domain. As shown, the embodimentOFDMA frame 700 comprises a plurality of OFDMA subframes 705, 710, 715,720 communicated over different sub-channels. Each of the OFDMAsubframes 705, 710, 715, 720 includes a preamble 701, a HEW preamble702, and a HEW data region 703. The preamble field 701 may be similar tothe preamble field 252 in the embodiment DL OFDMA frame structure 200.The HEW data region 703 may carry physical layer convergence protocolservice data units (PSDUs) destined for one or more STAs.

The OFDMA subframes 705, 710, 715, 720 may carry different numbers ofSTSs in the HEW data region 703. In this example, the OFDMA sub-frame705 carries two STSs for each of a first STA (STA1) and a second STA(STA2). The OFDMA sub-frame 710 carries one STS for each of a third STA(STA3) and a fourth STA (STA4). The OFDMA subframes 715, 720 each carryone STS for a fifth STA (STA5) and a sixth STA (STA6), respectively.

Notably, while the OFDMA subframes 705, 710, 715, 720 carry differentnumbers of STSs, they nevertheless include the same number of HEW-LTFs.More specifically, the number of HEW-LTFs carried in each OFDMAsub-frame is determined by the number of HEW-LTFs needed for the OFDMAsub-frame carrying the most STSs. In this example, the OFDMA sub-frame705 carries the highest number of STSs (i.e., 4 STSs), and consequentlythe number of HEW-LTFs carried by the OFDMAs sub-frame 710, 715, 720 aredetermined based on the number of HEW-LTFs needed for the OFDMAsub-frame 705 (i.e., 4 HEW-LTFs). Put differently, IEEE 802.11acrequires four HEW-LTFs 706 to communicate the OFDMA sub-frame 705carrying four STSs, two HEW-LTFs 711 to communicate the OFDMA sub-frame710 carrying two STSs, one HEW-LTF 716 to communicate the OFDMAsub-frame 715 carrying one STS, and one HEW-LTF 721 to communicate theOFDMA sub-frame 720 carrying one STS. The embodiment frame formatprovided herein includes two additional HEW-LTFs 712 in the OFDMAsub-frame 710, and three additional HEW-LTFs 717, 722 in each of theOFDMA subframes 715, 720, so that the LTF sections of the OFDMAsubframes 710, 715, 720 align with the LTF section of the OFDMAsub-frame 705. Accordingly, LTF sections in the OFDMA subframes 705,710, 715, 720 may be aligned in the time domain by virtue of the samenumber of LTFs having been generated for each of the OFDMA subframes.Advantageously, the additional HEW-LTFs 712, 717, 722 carried by theOFDMA subframes 710, 715, 720 provide for improved channel estimationupon reception.

In a multi-preamble type of DL OFDMA frame structure, the HEW-STFs andthe sets of HEW-LTFs precede the data fields carried in a sub-frame. Thenumbers of HEW-STFs, as well as the number of sets of HEW-LTFs, dependon how many data fields are carried in the sub-frame. Respective sets ofHEW-LTFs in different subframes may be aligned in the time domain usingLTF extension techniques described above. For example, if two subframescarry data fields in the same time slot that are transmitted usingdifferent numbers of TX streams, then a first data field (e.g., the datafield transmitted using more TX streams) may require more LTFs than asecond data field transmitted using fewer TX streams). LTF extension maybe achieved by including extra LTFs in the set of LTFs corresponding tothe second data field such that the sets of LTFs for both data fieldshave the same number of LTFs. In this way, the sets of LTFs may have thesame length, and may therefore be aligned in the time domain. Theadditional LTFs in the set of LTFs for the second data field may allowfor improved channel estimation by mobile stations scheduled to receivedata in the second data field. Thus, the extra LTF fields may not beconsidered wasteful overhead, and may provide performance benefits overzero padding. The performance improvement with the p-matrix LTFextension was demonstrated in U.S. Provisional Patent Application No.62/028,174.

U.S. Provisional Patent Application No. 62/028,208 proposed an OFDMA RUto be composed of 26 subcarriers by 8 symbols. Aspects of thisdisclosure provide an Interleaver/de-interleaver pair with the 26×2symbols, 26×4 symbols, or 26×8 symbols unit. Since the size of anInterleaver/de-interleaver unit is 52, 104, or 208 in BPSK and 1 Spatialstream, it is possible to re-use the current 802.11 20 MHz Interleaver.However, the input bits may be read into the embodiment Interleavercolumn by column, and may be written into the input port of 802.11 20MHz Interleaver, row by row. As for de-interleavers, the procedure willbe opposite. The output bits out of the current 802.11 20 MHzde-interleaver can be read out row by row, and written onto the outputport of the embodiment de-interleaver.

In one example, a 26×2 unit Interleaver is provided. In case of 16-QAMand 8 spatial stream case, a 26×2×4 (4 bits per 16-QAM)×8 (8 spatialstreams) binary bit stream is provided (that is, 1664 total bits). Sincethere are two columns in case of 26×2 unit Interleaver, total 1664binary bits are serially taken, and the index of which are re-arrangedas the even numbered index first and the odd numbered index thefollowing. The even index (0, 2, 4, etc.) is first and the odd index(e.g., 1, 3, 5, etc.) follows. The index of incoming binary bits can bere-arranged, after which the 802.11 20 MHz Interleaver can beoperated/run with the same NCOL, NROW, NROT, ISS parameters used in the802.11 specification. The de-interleaver procedure will be the opposite.The de-interleaver will take the incoming data and run through the802.11 20 MHz de-interleaver with the same parameters as in the 802.11specification. The index of this output data will be re-arranged. Thede-interleaver output will be passed over to the next function block,channel decoder. FIG. 8 shows the graphical representation of the givenexample above.

Embodiment interleavers may provide diversity over the OFDM(A) symbols,that is, time. The existing interleaver in 802.11ac provides theinterleaving over the frequency tones and spatial domain (over themultiple streams). Embodiment interleavers provide the interleaving overthe symbols in addition to over the frequency tones, and spatialstreams.

Aspects of this disclosure provide performance improvement with the toneinterleaved LTF when using more LTFs than are otherwise required. In thecurrent 802.11 specification, the number of long training fields (LTF)is determined by the number of TX (Transmission) space-time streams orthe number of TX antennas (in case of Channel Sounding). That is, incase the number of TX space-time streams is 1, 2, 3, 4, 5, 6, 7, or 8,the number of LTFs is required to be 1, 2, 4, 4, 6, 6, 8, or 8,respectively, corresponding to the number of TX space-time streams abovein the 802.11ac specification.

Aspects of this disclosure introduce embodiment LTF designs including atone interleaved LTF (TIL), in which a similar principle to decide thenumber of LTFs may be applied. Aspects of this disclosure useinterpolation techniques to estimate the channel using the TIL. Asmaller number of LTFs may be used when applying an interpolation schemeto estimate the channel.

Aspects of this disclosure extend the number of LTFs even with the TIL.The same number of LTFs as the number of TX space-time streams (STS) fordown-link (DL) or the number of STAs for up-link (UL) may be doubledlike the p-matrix based LTFs. That is, for 4 TX STS in case of DL or for4 STAs in case of UL, it may be possible to use 4 TILs to estimate thechannel without interpolation. However, it when 8 TILs for 4 TX STS (DLcase) or 4 STAs (UL case) are used, it is possible to achieveapproximately 1.5 dB Packet Error Rate (PER) Performance gain.

Aspects of this disclosure may use more LTFs than required to achievethe error rate performance improvement even with the TIL. For example,for 2 TX space-time streams (for DL), 2 LTFs may be enough to estimatethe channel with the TIL, but embodiment we apply 4 LTFs to achievebetter performance for the 2 TX streams case. The same principle may beapplied to the different number of TX streams or to the UL transmission.

FIG. 9 illustrates a graph of simulation results showing the PacketError Rate (PER) comparison between with 4 LTFs and with 8 LTFs for bothTIL based Channel estimation and p-matrix based Channel estimation. Thesimulation is run for the UL MU-MIMO system with 3 STAs, each having 1TX antenna and stream over the IEEE channel D. The AP has 4 RX antennas.As shown, the same UL MU-MIMO system with 8 LTFs shows the 1.5 dB gainover the UL MU-MIMO with 4 LTFs.

Aspects of this disclosure provide embodiment OFDMA AcknowledgementProcedures. In wireless LAN setup, the integrity of the transmitted dataframes is acknowledged by the receiver by sending an ACK frame or aBlock ACK (BA) frame back to the sender. An ACK frame provides theacknowledgement for a single data unit, while a BA frame provides theacknowledgement for a block of data units. Additionally acknowledgementsmay be sent immediately after the reception of the data unit (or a blockof data units) or they may be sent as a response to a Block ACK Request(BAR) sent by the transmitter. The type of the ACK is determined by theACK policy bits in the QoS Control field.

Aspects of this disclosure provide two embodiment methods for OFDMA ACKprocedure, namely an immediate acknowledgement procedure and anon-immediate or mixed acknowledgement procedure. FIG. 10 illustrates adiagram of an embodiment immediate acknowledgement procedure. In orderto have OFDMA Immediate Acknowledgement, all data units in the OFDMAPPDU may have their ACK policy indicating this variant of the ACK (bysetting bit #5 to zero and bit #6 to zero in the QoS Control field).With OFDMA Immediate Acknowledgements, stations (STAs) that havereceived data units from the AP starts sending their BA using UL OFDMAformat Short Inter-Frame spacing (SIFS) time units after the conclusionof the OFDMA PPDU. They use the same sub-carriers used by the AP totransmit their respective data units. Regarding non-immediate (mixed)acknowledgements. In different scenarios where not all the data unitsare requesting immediate acknowledgements, the AP may use BAR frames inorder to solicit acknowledgements from STAs that are not requestingimmediate ACKs. FIG. 11 illustrates a diagram of an embodiment OFDMAMixed Acknowledgement. STAs for which immediate ACK indication is setstarts sending their BA frames SIFS time after the end of the OFDMAPPDU. STAs for which the immediate ACK indication is not set waits for aBAR frame received from the AP. Both the BAR and the BA frames are sentusing OFDMA format.

FIG. 12 illustrates a block diagram of an embodiment processing system1200 for performing the methods described herein, which may be installedin a host device. As shown, the processing system 1200 includes aprocessor 1204, a memory 1206, and interfaces 1210-1214, which may (ormay not) be arranged as shown in FIG. 12. The processor 1204 may be anycomponent or collection of components adapted to perform computationsand/or other processing related tasks, and the memory 1206 may be anycomponent or collection of components adapted to store programmingand/or instructions for execution by the processor 1204. In anembodiment, the memory 1206 includes a non-transitory computer readablemedium. The interfaces 1210, 1212, 1214 may be any component orcollection of components that allow the processing system 1200 tocommunicate with other devices/components and/or a user. For example,one or more of the interfaces 1210, 1212, 1214 may be adapted tocommunicate data, control, or management messages from the processor1204 to applications installed on the host device and/or a remotedevice. As another example, one or more of the interfaces 1210, 1212,1214 may be adapted to allow a user or user device (e.g., personalcomputer (PC), etc.) to interact/communicate with the processing system1200. The processing system 1200 may include additional components notdepicted in FIG. 12, such as long term storage (e.g., non-volatilememory, etc.).

In some embodiments, the processing system 1200 is included in a networkdevice that is accessing, or part otherwise of, a telecommunicationsnetwork. In one example, the processing system 1200 is in a network-sidedevice in a wireless or wireline telecommunications network, such as abase station, a relay station, a scheduler, a controller, a gateway, arouter, an applications server, or any other device in thetelecommunications network. In other embodiments, the processing system1200 is in a user-side device accessing a wireless or wirelinetelecommunications network, such as a mobile station, a user equipment(UE), a personal computer (PC), a tablet, a wearable communicationsdevice (e.g., a smartwatch, etc.), or any other device adapted to accessa telecommunications network.

In some embodiments, one or more of the interfaces 1210, 1212, 1214connects the processing system 1200 to a transceiver adapted to transmitand receive signaling over the telecommunications network. FIG. 13illustrates a block diagram of a transceiver 1300 adapted to transmitand receive signaling over a telecommunications network. The transceiver1300 may be installed in a host device. As shown, the transceiver 1300comprises a network-side interface 1302, a coupler 1304, a transmitter1306, a receiver 1308, a signal processor 1310, and a device-sideinterface 1312. The network-side interface 1302 may include anycomponent or collection of components adapted to transmit or receivesignaling over a wireless or wireline telecommunications network. Thecoupler 1304 may include any component or collection of componentsadapted to facilitate bi-directional communication over the network-sideinterface 1302. The transmitter 1306 may include any component orcollection of components (e.g., up-converter, power amplifier, etc.)adapted to convert a baseband signal into a modulated carrier signalsuitable for transmission over the network-side interface 1302. Thereceiver 1308 may include any component or collection of components(e.g., down-converter, low noise amplifier, etc.) adapted to convert acarrier signal received over the network-side interface 1302 into abaseband signal. The signal processor 1310 may include any component orcollection of components adapted to convert a baseband signal into adata signal suitable for communication over the device-side interface(s)1312, or vice-versa. The device-side interface(s) 1312 may include anycomponent or collection of components adapted to communicatedata-signals between the signal processor 1310 and components within thehost device (e.g., the processing system 1200, local area network (LAN)ports, etc.).

The transceiver 1300 may transmit and receive signaling over any type ofcommunications medium. In some embodiments, the transceiver 1300transmits and receives signaling over a wireless medium. For example,the transceiver 1300 may be a wireless transceiver adapted tocommunicate in accordance with a wireless telecommunications protocol,such as a cellular protocol (e.g., long-term evolution (LTE), etc.), awireless local area network (WLAN) protocol (e.g., Wi-Fi, etc.), or anyother type of wireless protocol (e.g., Bluetooth, near fieldcommunication (NFC), etc.). In such embodiments, the network-sideinterface 1302 comprises one or more antenna/radiating elements. Forexample, the network-side interface 1302 may include a single antenna,multiple separate antennas, or a multi-antenna array configured formulti-layer communication, e.g., single input multiple output (SIMO),multiple input single output (MISO), multiple input multiple output(MIMO), etc. In other embodiments, the transceiver 1300 transmits andreceives signaling over a wireline medium, e.g., twisted-pair cable,coaxial cable, optical fiber, etc. Specific processing systems and/ortransceivers may utilize all of the components shown, or only a subsetof the components, and levels of integration may vary from device todevice.

Although the description has been described in detail, it should beunderstood that various changes, substitutions and alterations can bemade without departing from the spirit and scope of this disclosure asdefined by the appended claims. Moreover, the scope of the disclosure isnot intended to be limited to the particular embodiments describedherein, as one of ordinary skill in the art will readily appreciate fromthis disclosure that processes, machines, manufacture, compositions ofmatter, means, methods, or steps, presently existing or later to bedeveloped, may perform substantially the same function or achievesubstantially the same result as the corresponding embodiments describedherein. Accordingly, the appended claims are intended to include withintheir scope such processes, machines, manufacture, compositions ofmatter, means, methods, or steps.

What is claimed is:
 1. A method comprising: transmitting, by a firststation (STA), first information in a uplink (UL) orthogonal frequencydivision multiple access (OFDMA) sub-frame over a wireless network,wherein the UL OFDMA sub-frame carries a first data field from the firstSTA in a first time segment of a OFDMA sub-channel, a second data fieldfrom a second STA in a second time segment of the OFDMA sub-channel, afirst high efficiency wireless local area network (HE WLAN) (HEW) shorttraining field (STF) for the first data field, a first set of HEW longtraining fields (LTFs) for the first data field, and a second set of HEWLTFs for the second data field.
 2. The method of claim 1, wherein thefirst HEW STF and the first set of HEW LTFs precede the first data fieldin the time domain, and the second set of HEW LTFs are positioned inbetween the first data field and the second data field in the timedomain.
 3. The method of claim 1, wherein the UL OFDMA sub-framecomprises a preamble field and a HEW SIGA/SIGB field, the preamble fieldcarrying information for mobile stations operating in accordance withInstitute of Electrical and Electronics Engineers (IEEE) 802.11n.
 4. Themethod of claim 1, wherein the first data field is transmitted usingdifferent beamforming parameters than the second data field.
 5. Themethod of claim 4, wherein the first set of HEW LTFs are transmittedusing the same beamforming parameters as the first data field, andwherein the second set of HEW LTFs is transmitted using the samebeamforming parameters as the second data field.
 6. The method of claim1, wherein the UL OFDMA sub-frame further carries a second HEW STF forthe second data field.
 7. A first station (STA) comprising: a processor;and a computer readable storage medium storing programming for executionby the processor, the programming including instructions to: transmitfirst information in a uplink (UL) orthogonal frequency divisionmultiple access (OFDMA) sub-frame over a wireless network, wherein theUL OFDMA sub-frame carries a first data field from the first STA in afirst time segment of a OFDMA sub-channel, a second data field from asecond STA in a second time segment of the OFDMA sub-channel, a firsthigh efficiency wireless local area network (HE WLAN) (HEW) shorttraining field (STF) for the first data field, a first set of HEW longtraining fields (LTFs) for the first data field, and a second set of HEWLTFs for the second data field.
 8. The first STA of claim 7, wherein thefirst HEW STF and the first set of HEW LTFs precede the first data fieldin the time domain, and the second set of HEW LTFs are positioned inbetween the first data field and the second data field in the timedomain.
 9. The first STA of claim 7, wherein the UL OFDMA sub-framecomprises a preamble field and a HEW SIGA/SIGB field, the preamble fieldcarrying information for mobile stations operating in accordance withInstitute of Electrical and Electronics Engineers (IEEE) 802.11n. 10.The first STA of claim 7, wherein the first data field is transmittedusing different beamforming parameters than the second data field. 11.The first STA of claim 10, wherein the first set of HEW LTFs aretransmitted using the same beamforming parameters as the first datafield, and wherein the second set of HEW LTFs is transmitted using thesame beamforming parameters as the second data field.
 12. The first STAof claim 7, wherein the UL OFDMA sub-frame further carries a second HEWSTF for the second data field.
 13. A method comprising: receiving, by afirst station (STA), a downlink (DL) orthogonal frequency divisionmultiple access (OFDMA) sub-frame, wherein the DL OFDMA sub-framecarries a first data field for the first STA in a first time segment ofan OFDMA sub-channel, a second data field for a second STA in a secondtime segment of the OFDMA sub-channel, a first high efficiency wirelesslocal area network (HE WLAN) (HEW) short training field (STF) for thefirst data field, a first set of HEW long training fields (LTFs) for thefirst data field, and a second set of HEW LTFs for the second datafield.
 14. The method of claim 13, wherein the first HEW STF and thefirst set of HEW LTFs precede the first data field in the time domain,and the second set of HEW LTFs are positioned in between the first datafield and the second data field in the time domain.
 15. The method ofclaim 13, wherein the DL OFDMA sub-frame comprises a preamble field anda HEW SIGA/SIGB field, the preamble field carrying information formobile stations operating in accordance with Institute of Electrical andElectronics Engineers (IEEE) 802.11n.
 16. The method of claim 13,wherein the first data field is received using different beamformingparameters than the second data field.
 17. The method of claim 16,wherein the first set of HEW LTFs are received using the samebeamforming parameters as the first data field, and wherein the secondset of HEW LTFs is transmitted using the same beamforming parameters asthe second data field.
 18. The method of claim 13, wherein the DL OFDMAsub-frame further carries a second HEW STF for the second data field.19. A first station (STA) comprising: a processor; and a computerreadable storage medium storing programming for execution by theprocessor, the programming including instructions to: receive a downlink(DL) orthogonal frequency division multiple access (OFDMA) sub-frame,wherein the DL OFDMA sub-frame carries a first data field for the firstSTA in a first time segment of an OFDMA sub-channel, a second data fieldfor a second STA in a second time segment of the OFDMA sub-channel, afirst high efficiency wireless local area network (HE WLAN) (HEW) shorttraining field (STF) for the first data field, a first set of HEW longtraining fields (LTFs) for the first data field, and a second set of HEWLTFs for the second data field.
 20. The first STA of claim 19, whereinthe first HEW STF and the first set of HEW LTFs precede the first datafield in the time domain, and the second set of HEW LTFs are positionedin between the first data field and the second data field in the timedomain.
 21. The first STA of claim 19, wherein the DL OFDMA sub-framecomprises a preamble field and a HEW SIGA/SIGB field, the preamble fieldcarrying information for mobile stations operating in accordance withInstitute of Electrical and Electronics Engineers (IEEE) 802.11n. 22.The first STA of claim 19, wherein the first data field is receivedusing different beamforming parameters than the second data field. 23.The first STA of claim 22, wherein the first set of HEW LTFs arereceived using the same beamforming parameters as the first data field,and wherein the second set of HEW LTFs is transmitted using the samebeamforming parameters as the second data field.
 24. The first STA ofclaim 19, wherein the DL OFDMA sub-frame further carries a second HEWSTF for the second data field.